1. Field of the Invention
The invention relates to a light emitting element array module and a printer head and a micro-display using the module.
2. Description of the Related Art
Light emitting diode (LED) arrays are widely used in printer heads of printing machines or copying machines. A typical LED printer head includes an LED unit, an optical element for focusing light rays emitted from the LED unit, and a support portion for holding the LED unit and the optical element. As shown in FIGS. 1 and 2, a conventional LED unit includes a printed circuit board 1, a plurality of LED array chips 2 and a plurality of driving devices 3. The LED array chips 2 are connected with one another to achieve a required length for the printer head and are mounted on a component surface of the printed circuit board 1. The driving devices 3 are disposed in a row on the component surface of the printed circuit board 1 and in parallel with the LED array chips 2. Each driving device 3 is electrically connected to one of the LED array chips 2 by bonding wires 4, and to conductive patterns 5 on the printed circuit board 1 by bonding wires 6.
In the LED array chip 2, each LED emitting area 20 is very small, and the density of the LED emitting areas 20 is high. For example, if a resolution of 600 dpi is to be achieved, about 5000 sites of the LED emitting areas 20 must be formed on one chip 2. Then, a wire bonding process must be performed for each bonding pad 21. That is, the wire bonding process must be performed for about 5,000 times to form the bonding wires 4. In this case, since the number and the density of the bonding wires 4 are so large that the manufacturing process becomes difficult, resulting problems such as a lowered yield and an increased manufacturing cost.
To solve the above-mentioned problems, the invention provides a light emitting element array module including: a board; a silicon base having at least a first side, a second side, a third side, a fourth side and a fifth side, wherein the second side is opposite to the first side and has a first included angle with the third side, the fourth side is substantially in parallel with the first side and has a second included angle with the third side, the fourth side has a third included angle with the fifth side, and the second side is adhered to the board; a chip having a first main surface and a second main surface, wherein on the first main surface is formed with at least one light emitting element array and at least one pad array, the pad array is connected to the fourth side of the silicon base, and the second main surface is adhered to the board; a driving device for driving the at least one light emitting element array, wherein the driving device is adhered to the first side of the silicon base; and a plurality of metal wires each formed on the first, fourth and fifth sides of the silicon base, for connecting the at least one pad array of the chip to the driving device.
According to the light emitting element array module of the invention, the idea of xe2x80x9cflip chip bondingxe2x80x9d is used instead of a complicated wire bonding process, thereby reducing the manufacturing cost. In addition, in the light emitting direction of the light emitting element array module of the invention, there exists no other elements and thus the light rays emitted from the light emitting element array module are not blocked nor interfered by other elements. Therefore, the light emitting element array module of the invention has both the advantages of low manufacturing cost and excellent light emitting quality.